Catalyst system for use in nitric acid oxidation of olefins

ABSTRACT

Olefins are oxidized to carboxylic acids by contacting the olefins in the liquid phase with nitric acid in the presence of a catalyst consisting of vanadium and silver ions.

United States Patent Wasecheck 51 Sept. 19, 1972 [54] CATALYST SYSTEM FOR USE IN [56] References Cited NITRIC ACID OXIDATION OF U E OLEFINS NITED STAT s PATENTS 2,995,528 8/1961 Dowder et a1 ..210/533 R x Paul H. Wasecheck, Canterbury, Okla. 74601 Assignee: Continental Oil Company, Ponca City, Okla.

Filed: Feb. 22, 1971 Appl. No.: 117,793

Inventor:

US. Cl. ..260/4l3, 260/533 R Int. Cl ..C07c 51/32 Field of Search ..260/413, 533 R 3,549,696 12/1970 Duraux et al. ..260/533 R Primary Examiner-Lorraine A. Weinberger Assistant Examiner-Richard D. Kelly Attorney-Joseph C. Kotarski, Henry H. Huth, Robert B. Coleman, Jr. and Gerald L. Floyd ABSTRACT Olefins are oxidized to carboxylic acids by contacting the olefins in the liquid phase with nitric acid in the presence of a catalyst consisting of vanadium and silver ions.

1 1 Claims, No Drawings CATALYST SYSTEM FOR USE IN NITRIC ACID OXIDATION OF OLEFINS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to the production of carboxylic acids by the nitric acid oxidation of olefins, and more particularly, to the catalysis of such oxidations to improve the yield of carboxylic acids, and the selectivity as between the carboxylic acids produced.

2. Brief Description of the Prior Art [t is well known that various hydrocarbons, including olefinic compounds, can be oxidized in the vapor phase by contacting them with an oxygen-containing gas in the presence of a catalyst system which includes vanadium ions, and ions of another metal, such as silver. Thus, in U. S. Pat. No. 2,995,528, the catalyst system prescribed is a vanadyl vanadate of silver in which the ratio of vanadium oxide to the complexed metal oxide is preferably within certain limits. The vapor phase oxidation is carried out at a temperature exceeding about 250 C.

In the hydrocarbon oxidation process described in U.

S. Pat. No. 3,277,017, thecatalyst used is a vanadium oxide-molybdenum oxide system modified with a small amount of silver orthophosphate. The vapor phase oxidations using this catalyst system are carried out at temperatures exceeding 400 C. Some advantage is stated to be derived from the addition of small amounts of silver nitrate to the catalyst system, but the main benefit derived from this material occurs when it is used conjunctively with the larger amount of silver orthophosphate, or at temperatures below 444 C, at which temperature it undergoes decomposition.

U. S. Pat. No. 3,395,159 describes an oxidation catalyst system which includes vanadium oxide and up to'about 40 weight per cent of a heavy metal oxide, such as silver oxide. The oxidation of vaporized hydrocarbons at temperatures of from about 300 C to about 650 C is carried out in the presence of this catalyst system.

SUMMARY OF THE PRESENT INVENTION The present invention provides a method for oxidizing olefins in the liquid phase to carboxylic acids. The process can be carried out at relatively low temperatures, and excellent yields of carboxylic acids are realized.

Broadly described, the process comprises contacting olefins in the liquid phase with nitric acid in the presence of a catalyst consisting essentially of vanadi um and silver ions. The reaction is carried out at a temperature of from about 20 C to about 1 C.

An object of the invention is to provide a process for oxidizing olefins in the liquid phase to carboxylic acids so as to obtain better yields of the acid product than can be obtained using either vanadium or silver as a catalyst or promoter material.

Another object of the invention is to provide a method for oxidizing olefins at a relatively low temperature to realize good yields of carboxylic acids.

Additional objects and advantages of the invention will become apparent as the following detailed description of the invention is read.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION The olefins oxidized by the process of the present invention may be terminal or internal olefins, and may be of branched or straight chain molecular structure. The l-olefins respond especially well to the process.

The oxidation of olefins is accomplished by contacting them with nitric acid. The acid may have a strength ranging from about 8 molar to about 21 molar, with acid strengths of from 12 molar to 16 molar being preferred. The reaction is carried out at temperatures of from about 20 C to about 110 C, and preferably from about 35 C to about 100 C. Some benefit is derived from conducting the reaction initially at a relatively low temperature, following by completion of the reaction at a relatively higher temperature. A reaction period of from 1 to 4 hours is preferably utilized.

The catalyst system includes vanadium and silver ions. The vanadium and silver may be present as free metals or as compounds. In typical practice of the invention, silver nitrate in combination with either ammonium vanadate or vanadium pentoxide has, for example, been used with good success. An effective amount of the catalyst is utilized, and may. vary widely depending on reaction conditions. The vanadium, however, is preferably utilized in an amount of from about 0.005 equivalent to about 0.5 equivalent per mole of olefin to be oxidized, and the silver is preferably utilized in an amount of from about 0.001- equivalent to about 0.5 equivalent per mole of olefin starting materi al. A nitrite salt or N0 may be utilized as a reaction initiator if desired.

The process of the present invention provides the advantage of permitting the olefin oxidation to be carried out in the liquid phase, and at relatively low temperatures as compared to the elevated temperatures at which oxidations in the vapor phase by oxygen containing gases are conducted. MOreover, at the temperatures utilized, relatively inexpensive silver salts, such as silver nitrate, which melt or decompose at relatively low temperatures can be employed. Finally, and quite importantly, as compared to prior usages of vanadiumsilver catalyst systems in vapor phase oxidations, good yields of carboxylic acids, as contrasted with aldehydes and ketones, are realized from the catalyzed nitric acid oxidation.

Although the catalytic or reaction promoting role of vanadium in nitric acid oxidations of hydrocarbons has been previously appreciated, a synergistic effect has been discovered to characterize the vanadium-silver system. The following examples demonstrate typical practice of the invention, and also clearly illustrate the synergism which is characteristic of the dual metal catalyst.

EXAMPLE 1 A three-necked, round-bottom flask equipped with condenser, thermometer, mechanical stirrer and addition funnel was charged with 500 ml of 15.4 molar nitric acid. Ammonium vanadate, or silver nitrate, or both, where used, were then added to the flask. The reaction mixture was then heated to C. 35 grams of l-octene were next added to the flask in a drop-wise manner. The reaction was carried out for a period of four hours as measured from the commencement of the olefin addition.

The reaction product was extracted with pentane, and the carboxylic acids were then isolated from the pentane by base extraction. The carboxylic acids were then analyzed using decanoic acid as an internal standard, with conversion of the acids to the esters, and quantitative gas chromatography of the esters. The results of these oxidations are set forth in Table l.

TABLE I Product yield, Acid distribution, weight percent weight percent NILjVOfl, AgNO;

Run moles moles Acids Non-acids Ca Ca 01 Total 68. 3 10. 9 7. 3 2T. 64. 0 98. 3 80. 2 11.7 3.7 18. 4 7G. 0 90. 0 G5. 8 3. 5 7. 0 39. 5 30.7 78. 1 85.3 5. 4 3. 4 22. 8 71. 0 08.1

The data appearing in Table I show that the yield of carboxylic acids is increased when both the ammonium vanadate and silver nitrate are utilized as compared to the use of either the vanadium or silver compound alone.

EXAMPLE 2 The results of these runs are tabulated in Table 11.

TABLE 11 Product yield, Acid distribntion, weight percent, weight percent AKNOJ ltun moles Acids Non-maids Cr, C .(3 Total 5 87. '1 10.0 l. 'l lli. 4 71. 3 02. ll Ii 0. 02 .10. 1 7. 3 l. l 15. 3 70. 3 7 0. 01') .13. l 3. X l. 3 l7. 7 74L ii 113. 8 8 ll. 10 03. 1 3. .1 1. "l 18. i 75. U .14. 8

1 From Table 11 it may be seen that carrying out the reaction at two temperature levels (as contrasted with single temperature operation as described in Example 1) results in an increase in the total yield of carboxylic acids.

EXAMPLE 3 Another series of bi-level temperature oxidation runs of 35 grams of l-octene were carried out for a period of four hours using 500 ml of 14 molar nitric acid, 0.1 mole of sodium nitrite, and varying amounts of ammonium vanadate and silver nitrate. The variation in reaction conditions and results obtained in these runs are set out in Table III.

fore intended that modifications and innovations of the type described shall be encompassed by the spirit and scope of the invention, except as the same may be necessarily limited by the appended claims or reasonable equivalents thereof.

What is claimed is:

1. The method of oxidizing olefins to carboxylic acids which comprises contacting the olefins with nitric acid at a temperature of from about 20 C to about 110 C in the presence of a catalyst system consisting essentially of vanadium ions and silver ions.

2. The method defined in claim 1 wherein the nitric acid utilized has a strength of from about 8 molar to about 21 molar.

3. The method defined in claim 1 wherein the olefins are contacted with nitric acid at a temperature of from about 35 C to about C.

4. The method defined in claim 1 wherein the vanadium ions in the catalyst system are derived from a compound selected from the group consisting of ammonium vanadate and vanadium pentoxide.

5. The method defined in claim 1 wherein the silver ions in the catalyst are derived from silver nitrate.

6. The method defined in claim 1 wherein the amount of vanadium ion utilized in the catalyst system is from about 0.005 equivalent to about 0.5 equivalent per mole of the olefin contacted, and the amount of silver ion utilized in the catalyst system is from about 0.001 equivalent to about 0.5 equivalent per mole of the olefin contacted.

7. The method defined in claim 1 wherein the olefins are initially contacted with nitric acid in the presence of the catalyst at a temperature of about 35 C, and the temperature is then subsequently elevated to at least 95 C.

8. The method defined in claim 6 wherein the olefins are contacted with the nitric acid at a temperature of about 35 C for a period of from about 1 hour to about 2 hours, and is then contacted with the nitric acid at a temperature of at least 95 C for a period of from about 1 hour to about 2 hours.

TABLE III Tempem- Product yield, Acid distribution, ture, 0. weight percent, weight percent NHiVOa, AgNOx,

Run moles moles T1 T2 Acids Non-acids C5 C0 C Total about 2 hours, and is then contacted with the nitric acid at a temperature of at least C for a period of from I hour to about 2 hours.

1 l. The method defined in claim 10 wherein the strength of the nitric acid utilized is from about 8 molar to about 21 molar. 

2. The method defined in claim 1 wherein the nitric acid utilized has a strength of from about 8 molar to about 21 molar.
 3. The method defined in claim 1 wherein the olefins are contacted with nitric acid at a temperature of from about 35* C to about 100* C.
 4. The method defined in claim 1 wherein the vanadium ions in the catalyst system are derived from a compound selected from the group consisting of ammonium vanadate and vanadium pentoxide.
 5. The method defined in claim 1 wherein the silver ions in the catalyst are derived from silver nitrate.
 6. The method defined in claim 1 wherein the amount of vanadium ion utilized in the catalyst system is from about 0.005 equivalent to about 0.5 equivalent per mole of the olefin contacted, and the amount of silver ion utilized in the catalyst system is from about 0.001 equivalent to about 0.5 equivalent per mole of the olefin contacted.
 7. The method defined in claim 1 wherein the olefins are initially contacted with nitric acid in the presence of the catalyst at a temperature of about 35* C, and the temperature is then subsequently elevated to at least 95* C.
 8. The method defined in claim 6 wherein the olefins are contacted with the nitric acid at a temperature of about 35* C for a period of from about 1 hour to about 2 hours, and is then contacted with the nitric acid at a temperature of at least 95* C for a period of from about 1 hour to about 2 hours.
 9. The method defined in claim 8 wherein the vanadium ions and silver ions in the catalyst system are derived from ammonium vanadate and silver nitrate mixed with the nitric acid.
 10. The method defined in claim 9 whereiN the olefins are contacted with the nitric acid at a temperature of about 35* C for a period of from about 1 hour to about 2 hours, and is then contacted with the nitric acid at a temperature of at least 95* C for a period of from 1 hour to about 2 hours.
 11. The method defined in claim 10 wherein the strength of the nitric acid utilized is from about 8 molar to about 21 molar. 